TERRELL'S ISLAND: A CASE STUDY IN BIOLOGICAL AND CHEMICAL EFFECTS OF WATERFOWL ON FRESHWATER ENCLOSURES

Abstract

Although American White Pelicans (Pelecanus erythrorhynchos) (AWP) typically reside in the western plains of North America, within the last 30 years they have migrated to unexpected locations, perhaps due to climate change. One area of Wisconsin that has encountered unexpectedly high numbers of AWP (and other waterfowl) is Terrell's Island on Lake Butte des Morts, estimated to have over 1,500 nesting AWP. The presence of pelicans and other waterfowl is likely to have a significant, negative impact on recreational water quality in this area. Water samples were collected twice weekly from two sites around Terrell's Island on Lake Butte des Morts from inside the breakwall, directly adjacent to nesting islands, and from a "control" area in Shubert Marsh, away from pelican populations. A total of 24 samples were collected throughout the summer of 2012. Fecal indicator bacteria (FIB) were measured from both locations using the Colilert and Enterolert assays (for E. coli and enterococci, respectively). Each sample type was also filtered through nitrocellulose and polycarbonate filters for further microbial testing. Nitrocellulose filters were plated in triplicate onto various selective media to qualitatively identify potential pathogens (Salmonella, Campylobacter). Each set of polycarbonate filters was frozen at -80C to enumerate C. jejuni using quantitative PCR (qPCR). Equal numbers of samples were collected for both culture-based enumeration as well as molecular-based enumeration. Average culturable FIB concentrations were notably greater in waters adjacent to pelican nesting areas (E. coli: 480 vs. 76 MPN/100 ml, enterococci: 637 vs. 290 MPN/100 ml). Fecal pathogens (Salmonella, Campylobacter) were undetectable in water samples by traditional culture methods and by quantitative PCR (qPCR). On average, chlorophyll a concentrations were also considerably higher in the breakwall area compared to chlorophyll a concentrations in Shubert Marsh (119.83 vs. 92.74 g/L). In summary, AWP have a negative impact on water quality in Lake Butte des Morts and may impair recreational water quality at other locations with high waterfowl densities.